Apparatus for timing balances



April 13, 1937. 0 A. F. PQQLE 2,077,003

APPARHTUS FOR TIMING BALANCES 7 Filed Nov. 19, 1952 s"sheets-"sheet 1 Q l-NVENTOR April 13, 1937. v A. F. POOLE I 2,077,008

APPARATUS FOR TIMING BALANCES Filed Nov. 19, 1932 '3 Shegfs-Sheet 2 ulmnmulllllllu m INVENTOR Patented Apr. 13, 1937 V STATES PATENT OFFWE APPARATUS FOR TIMING BAIANCES Arthur F. Poole, Ithaca, N. 12.: Maryline B. Poole,

administratrix of said Arthur F. Poole, doceased, assignor to Maryline B. Poole, Ithaca,

Application Novemberli), 1932, Seriai No. 843,489

14 Claims. (or 73-51) 7 is to provide impulse means to keep the X balance in vibration while being tested, particularly in the provision of a pneumatic impulse 15 which will give impulse to the balance without having material connection therewith with the result that the impulse means requires no connection to the X balance when-the same is put into the testing fixture for timing.

Another object of my invention is the use of the hairspring of the x balance as a means of both keeping track of the time of vibrations of the X balance 'and also of determining the time of the pneumatic impulses to be given to said balance. Another object of .my invention is an improved impulse mechanism for a balance which has the function of automatically adjusting the effective impulse to the arc of the balance to the end of keeping the balance in a constant am- 30 plitude and avoiding'the isochronal error.

Another object of my invention is a phase changer to retard the phase of the standard impulses to bring them into phase with the impulses from the X balance whereby the two may 35 be compared. Another object of my invention is the use of a condenser circuit for comparing the X balance with the standard, and in" addition .so arranging this circuit that the indications thereof are given by a null method whereby va- 40 riations in the eiectromotive ,force, resistance of the contacts and the duration of the same affect only the sensitivity of the indications and not their null point.

Another object of my invention is an improved 45 fixture in which the X balance is mounted during test, details'of this fixture and the new points thereof will be set forth in the following description and claims. A further object of my invention is 'in the use of a triode and associated 50 circuits to translate the vibrations of the X balance into a series of electric currents which are compared in time to the standard impulses. A further object of my invention is an improved stroboscopic method of comparing the x bal- 55 shoes with the standard, both in the use of the usual sectored disc'and in a method using a jump spark to give the indication. A further object of my invention is in the provision of a muitivibrator circuit as a source of standard impulses and governing this circuit by a clock; the resulting current is then amplified and used to run synchronous motors at the several testing stations so that a single source of standard currents of small wattage may be used to provide standard currents for a large number of testing stations such as would be used in a factory. A further object of my invention is the provision of a standard current of small wattage and amplifying this current at a plurality of points to run synchronous motors for testing stations thereat.

The above and other objects of my invention will be apparent to those skilled in the art as theyv are set forth in the following specification and claims.

Before giving a detailed description of the apparatus shown in the accompanying drawings it will be of advantage to give a brief description of the theory on which my herein described apparatus is based. I provide a source of standard currents "from a master clock at the rate of 120 per minute, this being the rate of the particular balances described in this specification, and is taken merely for illustration on account of its being the rate of a common alarm clock, any other rate may be used to fit the time of the particular'balances to be timed. The standard" currents-are used to run a phase changer consisting of a synchronous motor which has a device to make a contact 120 times a minute also, however the contact making device "of the phase changer may be rotated, thereby changing the phase of said contacts as compared with the standard impulses. The purpose of this change will be apparent. presently.

The x balance is put in a fixture and started in vibration. This fixture has a clamp in which the end of the hairspring is fastened, a second clamp having the function of the hairspring stud, and a pair of regulator pins oneof which is insulated from the framework. The hairspring plays between these pins as the X balance vibrates. By a circuit, presently to be described, when the hairspring expands and makes contact with the insulated regulator pin. it works a relay. As so far described we have (a) a series of standard currents (b) a series of currents reproducing the vibrations of the-X balance (hereinafter called the xcurrents) and (0) means of bringing these two currents into phase, that is into co-incidence in time. The standard currents and the X ourrents are then led through a comparing circuit and associated galvanometer which will indicate the co-incidence in time of the two currents with any desired degree of exactness. When the currents are co-incident the galvanometer will be unmoved but as one current gains on the other the galvanometer. will be deflected to one side or the other, thereby indicating which set of currents is gaining on the other. The hairspring of the X balance is adjusted accordingly, the currents again brought into phase and a new observation made. When the currents remain in phase for a certain time the X balance is taken as ad justed. To mention some specific figures, in a certain comparator circuit described herein a difference of 1/ 150 second in the coincidence of the standard and X currents can certainly be detected. Therefore if the standard and X currents run for 10 seconds without preceptably departing from phase the X balance is adjusted. to an accuracy of better than one minute a day.

Referring now to the drawings, Fig. 1 is a diagrammatic layout of a preferredset of apparatus to carry out my invention, Fig. 2 is an elevation of part of the balance fixture, Fig. 3 is a, detail of Fig. 2, Fig. 4 is a modification of Fig. 1 and Fig. 2 particularly in certain portions of the fixture for the X balances, Fig. 5 shows a stroboscopi'c disc apparatus for comparison, Fig. 6 is a detail of Fig. 1, Fig. 7 is a multivibrator circuit used for standard currents in certain circumstances, and Fig. 8 is a modification of the stroboscopi'c apparatus which uses a jump spark as an indication of the frequency of the standard and X impulses. It is to be noted that the plan of the fixture shown in Fig. 1 is taken from below the line l-l of Fig. 2. "The same reference numerals refer to the-same parts in all the figures. In Fig. 1, I0 is a master clock preferably with a pendulum beating 120 beats per minute; it is furnished with some kind of a circuit making device (not shown) which makes the circuit including the relay I I and a battery I2 120 times a minute. There are. many devices suitable for this function in the prior art, I shall mention one shown in my Patent 1,310,374 of July 15, 1919. The relay H has an armature I 3 which serves to close a circuit from a battery l4 through field coils l5 and I6 of a phase changer H. A shaft l8 revolves on ball bearings in the framework of l1 and carries a permanent magnet l9 revolvms in the field of the coils l5 and IS. The arrangement constitutes a synchronous motor revolving R. P. M. in response to currents from the relay l l The motor has to be started manually. The shaft 3 also carries a flywheel 28 to give the moving system a large moment of in-' ertia The flywheel :28 is frictionally secured to the shaft l8 or may have the rim hollow and be filled with mercury whose friction will damp out sudden changes in the velocity of the shaft l8. The shaft l8 also carries a cam 2| of insulating material adapted to raise a spring 22 from a contact 23 for a given are of the revolution of the shaft l8; the spring 22 is mounted on and insulated from a wheel 24 which turns on'a sleeve 25 in the framework of H, said sleeve being concentric with the shaft I 8 but free from it. On the under side of the wheel 24 and insulated from it is a slip ring 26 connected to the spring 22 by a wire 21 and having a brush 28 in continuous contact therewith. The brush 28 is insulated from the framework of i1 and is connected by a wire 29 to one pole of the battery l4 the other pole of which is connected through a relay 30 to theframework of the phase changer I1. Each revolution of the shaft l8 accordingly results in the relay 30 attracting its armature 3 I. The currents, afterwards to be described, controlled by the relay 30 will hereinafter be called the standard currents since they reproduce the beats of the master clock [0. To provide for shifting the phase of the standard currents I have provided a pinion 32 meshing in the wheel 24 and mounted on a, shaft 33' turning in the framework of ll. A handle 34 is on the shaft 33 by which it may be turned for rotating the wheel 24 and the spring 22 and contact 23 mounted thereon thus c anging the time when the cam 2i breaks the circuit of the relay 30, and consequently changing the phase relation between the currents from the master clock I!) and those closed by the armature 3|.

While the rotation of the shaft 18 is not absolutely uniform, it being accelerated during the time of the action of the currents from the relay H on the magnet l9 and decelerated by friction during the remainder of its arc, yet as will be pointed out hereinafter, it is necessary only that the interval between two successive currents be one half a second. So long as the accelerations, plus and minus, do not change during the period of an observation the requirement of a constant interval between transits of the shaft l8 past a given point will be met nearly enough for my purpose. For regulation, I have provided an adjustable shunt 32' to vary the current to the coils l5 and It, so that the impulse may be suited to the load, this, in connection with the fly wheel 20 will keep the shaft l8 in rotation without undue hunting.

Passing for the moment description of the means by which the beats of the X balance are translated into a series of currents, assume that such a series are passed through a relay 33 havingan armature 34'. The armatures 3| and 34' are respectively connected to condensers 34 and 35, the other sides of said condensers being common to a battery 36 and windings 31 and 38 of a transformer 33. The winding 31 is joined to the front contact of the relay 33 and 38 is similarly joined to the front contact of the relay 38. The back contacts of these relays are joined to the other pole of the battery 36; from these circuits it results that the condensers 34 and 35 are charged to the potential of the battery 36 when the relay armatures 3i and 34 are in contact with their back stops. When said armatures are pulled to their front stops the condensers are discharged through the transformer windings 31 and 38 which are connected to induce currents in contrary senses in a winding 40 to which is connected a galvanometer 4l with an adjustable shunt 42. Assume that the discharge of the condenser 34, which is charged in step with the standard currents, gives the needle of the galvanometer 4| a kick to the minus side, and a discharge from the condenser' 35 kicks the needle to the plus side. The coils 31 and 38 and the condensers 34 and 35 are so adjusted that the simultaneous' discharge of both condensers results in no motion of the needle When the discharges get out of phase, the needle kicks to the one side followed immediately by a kick to the other side.

The magnitude of the kicks increases asthe imdischarge from the condenser 34 will give a kickin one direction. Similarly an unbalanced discharge from the condenser 35 will give a kick in the contrary direction. This, independent of the constants of the coils and condensers provided they are nearly equal, will give a null point at which the discharge of one condenser is neutralized by the discharge of the other. This point will gave a zero kick of the needle.

I will now describe the X balance fixture and circuits by which the vibrations of the balance are translated into a series of' currents through the relay 53. A framework 43 supports'an upper bearing 44 in which slides a rod 45 held in position by a spring 46 between a collar H on the rod 55 and the bearing. The lower end of the rod 55 has a socket for the X balance bearing and the upper end is threaded for an adjusting screw 55 which, by contact with the bearing 45 determines the position of the rod 55. A handle 59 on the rod 45 serves to withdraw it against the spring 55 when a new X balance is inserted.

An X balance 55 is mounted on a shaft 5i on which is-a collet 52 providing an attachment for the inner end of a hairspring 55. The lower bearing of the shaft 55 is in a stud 55 mounted in the framework 53. Rotatably mounted on the stud 55 is a wheel 55 which carries an upright 55 on which is a clamp 55 for the outer end of the hairspring 53.

40 collet 52 in order to pull the hairspring 55 into a cone shape to avoid interference with a second clamp 55 mounted on an arm 55 rigid with on a shaft 55 turning in the framework 55 and held by a spring M in contact with a spiral cam 55 rigid .with the wheel 55. A second arm 55 is on a shaft 55 turning in the framework 55 and is held by a spring 55' in contact with a second spiral cam 55 rigid with the cam 52 and therefore with the wheel 55. The arm 55 carries regulator 50 pins 55 and 51, the pin 55 being insulated from the framework 53. The hairspring plays between the pins 55 and 51! as the X balance vibrates; since the pin 55 is insulated irom'the framework, a circuit may be closed by the expansion of the spring 55 55 against said pin in a manner presently to be described. The regulator pins are placed the same angular distance from the clamp 55 as the regulator pins in the watch are placed from the hairspring stud (that is when the regulator is in its 0 center position) so as to get substantially the same conditions of regulator pins as will be had in the watch.

The wheel 55 to which is attached the clamp 51 and the cams 52 and 55 may be turned by a 5 pinion 55 on a shaft 55 turning and sliding in the framework 55 (Fig. 3) and held out of mesh with the wheel 55 by a spring W. The shaft 55 carries a collar H which engages a tail ill on the clamp 55 so as to disengage said clamp from the hairspring 7 53 when the wheel 55 is moved. A thumb nut l5 serves as a handle to turn the shaft 55.

The circuit by which the vibrations of the X balance are translated into vibrations of the relay armature includes a triode it having a plate 75 it, a grid 15 and a filament i5 with the usual The clamp 51! is mellow the A, B, and 0 batteries. Contact of the hairspring 53 with the regulator pin 61 throws a blocking potential from the C battery on the grid I5 thereby cutting down the plate current, or stopping it as the case may be. In the plate circuit is a. relay 11, for a purpose presently to be describedv and the relay 33. These relays are actuated in unison by flow of plate current when the grid I5 is unblocked, that is each time the X balance 50 vibrates.

The relay I1 closes a local circuit including a battery 18 and a solenoid 19, the latter on the frame 43. The solenoid 19 has a magnetic plunger 80 to which is a piston 81 working in a cylinder 82 and directing a jet of air tangentially against the X balance 50 through a nozzle 53 each time the piston is drawn up, that is each time the relay TI is drawn up. This air jet'keeps the X balance in vibration during test. A ball valve 84 admits air to the cylinder on the back stroke of the piston.

The operation of the complete device is as follows, the synchronous motor of the phase changer I1 is started and an X balance is put in the fixture 43, the hairspring is threaded through the regulator pins and gripped by the clamps 51 and 58.

When the balance is at rest the hairspring is adjusted to be out of contact with either regulato! pin. The balance is then started and kept going by the Jets of air from the nozzle 85. The needle of the galvanometer will kick. since in general the X balance will not be in phase with the standard impulses. The handle 55 is turned to bring the standard and X currents in phase, as

indicated by the galvanometer. However since the period of the X balance is not that of the standard the needle will start to kick to the one side or the other. The wheel 55 is turned by the nut i3 thereby changing the length of the hairspring. It will be observed that pressing the nut 175 to turn the wheel 55 will release the clamp 55. The two impulses are again brought to, phase and it will now be a longer time before they depart therefrom. This process is repeated until the two impulses stay in phase 10 seconds. This corresponds to an accuracy of a minute a day. The two cams 52 and 55 have the same pitch as the hairspring so as the wheel 55 is turned the regulator pins and the clamp 55 will keep their same relative positions to the spring 55.

It sometimes happens that--it is de red to adjust a balance whose hairspring does not conform to the spiral of the cams 52 and 55. For this case I use the structure shown in Fig. 4 in which the arms carrying the clip 55 and the regulator pins 55 and5i are adjustable. Referring to this figure an arm 95 (corresponding to the arm 55 of Fig. 1) is rigid on the shaft 55; turning on the same shaft is an arm 95 which carries the regulator pins 55 and 51, the latter insulated from said arm. The arms 93 and 55 are provided with tails 55 and 55 which are. pulled toward each other by a spring 95. The arm 53 carries a stud 55 in which is an adjusting screw I55 which bears against an ear 55 on v the thrust of a screw M'mounted in a stud 9i in the ar'm 55 which carries the clip 58. Thus the clip 55 may be adjusted independent of the cam 62 so that the hairspring may be centered. To adjust the clip 58 one turns the screw 02 until the hairspring is central. The regulator pins 61 and 66 may be adjusted by the sound of the relay TI which will beat evenly like a clock-in beat when the hairspring is central between the regulator pins.

Having described my preferred apparatus I shall now show some modifications of it. In 1Q Fig. 5 I have shown a stroboscopic disc IOI mounted on the shaft of the synchronous motor of the phase changer II, the contacts 22 and 23 are not used in this arrangement. The disc IOI is momentarily illuminated by a neon lamp I 02 lit by the discharge of a condenser I00 charged and discharged by the armature 34' of the relay 33. A battery I03 serves to charge the condenser to a voltage to light the lamp I02. The disc rotates at the standard rate or an integral multiple thereof. If the X balance is fast the disc will appear to turn in the direction of the shaft I8. If slow, it will appear to turn in the reverse direction. The nut 13 is adjusted until the disc appears stationary.

While the disc arrangement of Fig. 5 is simpler than the condenser arrangement of Fig. 1 it is not so good for continuous work. The intermittent flashing of the lamp is quite tiresome to the eyes of the operator.

An analogous arrangement is shown in Fig. 8.

in which the disc I 0| 'is replaced by a pointer I05 on the shaft I8 on which is an insulating washer I05 to which the pointer I05 is fastened. A brush IIJI' bears on a slip-ring I06 which is connected to the pointer I05 by a wire I08. An induction coil I08 has its high winding I01 connected to the brush I01, and hence to the pointer. I05, and to a ring I06 insulated from the framework. A condenser I0 3 is charged from a battery and discharged through a low winding I09 of the coil I08 by the relay 33, which it will be remembered is actuated in unison with the X balance. Each time the condenser is discharged a spark will jump from the pointer to the ring and indicate the instantaneous position of the pointer. The fact of the pointer spark remaining stationary will be an indication of the X balance. being in time with the standard impulses. Motion of the spark may be corrected by changing the length of the hairspring by rotating the wheel of the fixture 43. I have noted that the motion of the shaft under the currents from the clock I0 is not 55 rigorously uniform since there is but one impulse per revolution. For most commercial work this is accurate enough, however if higher accuracy is worth; the expense, increasing the currents per revolution of the shaft It will give it. To carry out this plan a source of regulated currents must be provided, if one uses a current of cycles per second the 2 cycle motor of the magnet I9 and the coils I5 and I6 is replaced by a 60 cycle synchronous motor.- Those used 5 for running clocks will answer very well. One suitable source of current is described in'vthe paper by Lewis on A clock controlled constant frequency generator in the Bureau of Standards Journal of Research for Jan. 1932. However a simpler and less costly way of securing a constant frequency current of 20 cycles per second is shown ,by me in Fig. '7. As before there is the clock I0 working a relay II 2 times per second and whose armature IIO serves to charge 5 a condenser M2 to the potential of a battery III and discharge the condenser through a winding II3 of a. transformer I I 4 whose winding II 5 serves to control a multivibrator circuit adjusted to oscillate 20 times per second. This circuit is well known in the radio art. It-consists of triodes H6 and III whose plates are connected through resistances IIS and lid to the positive pole of a battery I20 and whose grids are connected through resistances I22 and I23 to the negative pole of the battery I20 which is also common to the two filaments as shown. Condensers I24 and I25 connect the grid of each triode with the plate of the other. A full description of the action of this circuit may be found in Radio Engineering Principles, Lauer and Brown, 2nd. ed. pp. 208 et. seq. The circuit of the figure is adjusted to 20 oscillations per second and each tenth oscillation it receives a jolt from the discharge of the condenser IIZ which serves to wipe out the accumulated errors and start the oscillations in step with the clock again.

The current from the multivibrator is of small wattage and before being used to drive a synchronous motor must be amplified. To this end I have provided a transformer I21 to put the 20 cycle current on the grid of an amplifying tube I26 the plate current of which runs a synchronous motor I30 on the shaft I8 of a phase changer II or of the devices shown in Figs. 5 and 8. The wattage taken by the grid of the tube I26 is small, we may therefore have a second tube I28 amplifying current forya second motor I29 governed by the current from the transformer I27. This will be of use where there are a number of adjusting stations as in a factory. All may be governed by the same source of standard currents.

Another method of using the apparatus in Fig. 1 is founded on the fact that to a first approximation, the number of vibrations in a given time is inversely proportional to the length of the hairspring. Hence in testing a balance one may watch the galvanometer II a certain time (to be determined by experiment) keeping the needle stationary by turning the handle of the phase changer I'I. At the end of this time the phase changer has been rotated through a certain angle, if then the hairspring be changed the same angle by the handle 13 the balance will be nearly on time. To assist in this operation the handles 34 and 13 may be correspondingly graduated, and the balance may be brought to time in a couple of trials.

In Fig. 1, for the sake of clearness, the cam 2| and the spring 22 are much larger in proportion to the size of the phase changer I'I than these parts would be in practice where the cam 2i should have a radius about 1/20 of the radius of the wheel 20 and the spring 22 should be made as light as possible. This is to keep the load on the synchronous motor of the phase changer as light as possible. In some cases it may be of advantage to use a triode circuit for this contact as is shown in connection with the hairspring and triode 74. Such a modification may be readily made by those skilled in the art from the description of the circuit herein associated with the triode".

It will be noted in Fig. 8 that I have provided the ring I06 with graduations. These are for the purpose of noting the amount the Jump spark travels in a given time and thus obtain an indication of the error of the X balance. The hairspring 53 is then changed accordingly by means I spasms of the handle I3 which may be provided with suitable graduations. i

In some of the following claims I have used the term X balance by which I mean a balance 5 under test in the testing fixture 43. By the term X currents I mean a series of currents controlled by an X balance and kept in steptherewith. By the term standard currents" I mean a series of currents accurate as to time against which the X balance is checked.

The pneumatic impulse from the nozzle 83 has an automatic compensation to keep the balance at a constant arc. The effective impulse is due to the difference in velocity between the air jet and rim of the X balance on which the jet impinges. Increase of the balance are means increase of velocity and hence decreased impulse. So the balance are increases until it reaches a point where the effective impulse is equal to the inc tion losses and remains at that point.

I consider the use of a triode as a part of the apparatus for translating the vibrations of the x balance, or any balance, into a series of currents of great advantage. By its use I am enabled to take advantage of the contact of the hairspring itself with a pin insulated therefrom,

which pin may be in theposition of the ordinary regulator pin, to open and close the circuit in which flow the X currents. The clock hairspring is ordinarily of steel and coated witha blue oxide of iron, 9. bad and unreliable conductor of electricity. However by placing this hairspring contact in the grid circuit of a triode the current broken is of the ordero! a few micro-amperes, 5 and one may place a resistance of a megohm in the grid circuit without interfering with its certain and reliable action. A voltage wave blocks of! the plate current and there is no induction spark with its concomitant corrosion at the hair- 40 spring contact. Further, since the pinis in the place or the regulator pin the time of the balance is not changed.

In some of the .clairr is I, have referred to the instantaneous position or the balance. Since the balance must be in a certain position when the hairspring makes contact with the insulated pin 61, the resulting change or current, as shown by the action of the relay 33 is an indication of the position of--the balance at that instant.

Many changes may be made in the precise structure herein shown without departing from thescope of my invention, since I claim:- 1. In a device :ior testing balances, means operated by the balance to produce periodic elec- 55 tric impulses, a condenser, means to charge and discharge said condenser in step with said impulses, a standard source of electric impulses, a second condenser, means to charge and discharge said second condenser in step with said stand- 60 ard impulses, and means to detect a time interval between the discharge or said condensers. ;2. In a device .for testing balances, means operated by the balance for producing periodic electric impulses, a condenser, means to charge 65 and discharge said condenser in step with said impulses, a source of standard electric impulses, a second condenser, means to charge and discharge said second condenser in step with said standard impulses, and means to bring the dis- 70 charges of said condensers into coincidence.-

3. In a device for testing balances, means operated by the balance to produce periodic electric impulses,'a condenser, means to charge and discharge said condenser in step with said im- 75 pulse a source of standard electric impulses,

a second condenser, means to charge and discharge said second condenser in step with said standard impulses, and a galvanometer responsive to the discharge of both condensers to indicate a phase difference in the dischargeof said condensers.

4. In a balance testing apparatus, impulsing means for keeping the balance to be tested in vibration-without affecting the rate of vibration of said balance, a triode and an associated grid circuit containing a grid blocking potential and an associated plate circuit, means operated by said balance for opening said grid circuit, and means .in said plate circuit to operate said impulsing means.

5. In an apparatus for testing a balance and hairspring, a triodeand an associated grid circuit containing a grid blocking potential and an associatedplate circuit, anda fixed means co-operating with said hairspring for opening said grid circuit.

6. In an apparatus for testing a balance and hairspring, a triode and associated plate circuit and an associated grid circuit containing a grid blocking potential, a fixed means co-operating with said hairspring for opening said grid circuit, an electromagnet in said plate circuit, an armature associated with said electromagnet, whereby the vibrations of said balance are translated into motions of said armature.

'1. In a balance testing apparatus, a triode having a plate circuit and a grid circuit including a grid blocking potential, a fixed means operated by said balance to open said grid circuit in stepfwith said balance, means in said plate circuit to produce a series of impulses in step with said balance, a source of standard impulses, and means to detect a difference in phase of the two said sets of impulses.

8. In combination, a standard clock capable of producing a series of impulses, a motor driven in step with said impulses, a shaft driven by said motor, a set of contacts capable of being rotated around said shaft, support means for said contacts, means for causing a current to flow through said contacts, a cam on said shaft for opening said contacts as said shaft revolves, and manual means to shift said contact supporting means angularly around said shalt, whereby the impulses produced by virtue of the opening and closing of said contacts may be shifted in phase with respect to said standard impulses.

9. In an apparatus for testing a balance and hairspring, a fixed pin insulated from thehairspring and adapted to make contact therewith as the balance vibrates, a triode having a plate circuit associated therewith and a grid circuit containing a grid blocking potential, said grid circuit having said hairspring and pin in series therein to open and close said grid circuit in step with the'vibrations of said balanceand an electromagnet in said plate circuit.

10. In an apparatus for testing a balance and hair-spring, a triodehaving a plate circuit and a grid circuit containing a grid blocking potential,

a-fixed pin in said grid circuit adapted to be engaged by the hairspring as. the balance vi-' brates, and a relay and associated armature in said plate circuit whereby the vibrations of said balance are translated into actuations of said armature.

11. In a balance testing apparatusa triode having a plate circuit and a grid circuit including a grid blocking potential, a fixed means 0perated by said balance to open said grid circuit circuit to produce a series of impulses in step with said balance, a source of'standard impulses,

. a synchronous motor operated by said standard impulses, and means jointly operated by said synchronous motor and said balance impulses, whereby a difierence in phase of said balance impulses and said standard impulses may be detected.

12. In a device for testing balances, means operated by the balance for producing periodic electric impulses, a condenser, means to charge and discharge said condenser in step with said impulses, a source of standard electric impulses, impulse translating means operated by said standard impulses, a second condenser, means to charge and discharge said second condenser in step with said translated impulses,-and means whereby the charges on said two sets of condensers may be compared.

13. In a device for testing balances, means operated by the balance for producing periodic aov'agooe in step with said balance, means in said plateelectric impulses, a condenser, means to charge and discharge said condenser in step with said impulses, a source ofstandard'electric impulses, impulse translating means operated by said standard impulses, a second condenser, means to charge and discharge said second condenser in step with said translated impulses, and means responsive to the dischargevof both sets of condensers whereby a diiference in time of the discharges of said condensers may be observed.

14. In a device for testing balances, means operated by the balance to produce periodic electric impulses, a condenser, means to charge and discharge said condenser in step 'with said impulses, a standard source of electric impulses, a second condenser, means to charge and discharge said second condenser in step with said standard impulses, a common circuit responsive to the discharge of both condensers, and indicating means in said circuit.

ARTHUR F. POOLE. 

